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Thrombin functions through its RGD sequence in a non-canonical conformation.
Matthew E Papaconstantinou1, Christopher J Carrell, Agustin O Pineda
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
The Journal of Biological Chemistry
|July 7, 2005
Summary
Thrombin binding to endothelial cells via its RGD sequence promotes cell attachment and migration, independent of its catalytic activity. A novel crystal structure reveals an exposed RGD sequence in a non-canonical thrombin conformation.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Thrombin's RGD sequence was previously suggested to interact with endothelial cell integrins.
- Existing crystal structures show the RGD sequence buried, implying unfolding or digestion for interaction.
Purpose of the Study:
- To investigate thrombin's interaction with endothelial cells via its RGD sequence.
- To determine the role of the RGD sequence and catalytic activity in cell attachment and migration.
- To elucidate the structural basis for RGD-mediated interaction.
Main Methods:
- Site-directed mutagenesis of thrombin's RGD sequence.
- Assessing endothelial cell attachment and migration.
- Crystallography of thrombin under high salt conditions.
Main Results:
- Surface-bound thrombin promotes endothelial cell attachment and migration through alpha(v)beta(3) and alpha(5)beta(1) integrins.
- This effect is mediated by the RGD sequence and does not require thrombin's catalytic activity.
- A crystal structure revealed thrombin in an unprecedented conformation with an exposed RGD sequence.
Conclusions:
- Thrombin interacts with endothelial cells via its RGD sequence in a non-canonical conformation, independent of its enzymatic function.
- The exposed RGD sequence in this conformation facilitates cell adhesion and migration.
- Structural insights explain the mechanism of RGD-mediated integrin binding.